Alexander served as Naval Governor of Guam from February 8, 1938 to April 20, 1940.[7] Air travel became more prevalent during his tenure as more people traveled to the island from the mainland United States and air mail arrived frequently. He recommended various methods to make the island more defensible, including building additional warehouses and harbor facilities, dredging Apra Harbor, constructing a sea wall and oil storage facilities, and the erection of six new officers barracks.[8] He had to negotiate with the Japanese government in arranging the return of a number of Japanese fisherman who had been rescued when there ship Daichs Saiho Maru sunk in a restricted area of the Guamanian coast.[5] He also oversaw the 1940 United States Census on the island.[9]